Treasury Minister Cristobal Montoro told Spanish radio station Onda Cero that it is "technically impossible" for Spain to bail itself out. He said that Spain needs to get more money to improve its debt situation to open the bond markets back up so people can invest in the country.

"The risk premium says Spain doesn't have the market door open," said Montoro. "The risk premium says that as a state we have a problem in accessing markets, when we need to refinance our debt."

Economists estimate that the Spanish government has about €800 billion in outstanding debt.

Meanwhile, the European Stability Mechanism, a bailout fund that comes into effect this summer, will be equipped with only €500 billion.

"What's at stake is the euro and they must convince themselves and the markets that the euro is a reality and it does have a future," he said.

The minister's appeal comes as leaders from the Group of Seven nations met to discuss Europe's debt crisis. The G7 ministers and leaders agreed to keep close tabs on the situation ahead of the larger G20 meeting later this month, according to a U.S. Treasury statement.

The G7 comments may be helping prop up Spanish banking stocks, which have taken a pretty harsh beating this year. Shares of Banco Santander (STD) and BBVA (BBVA) both rose about 1.5% Tuesday. And the yield on Spain's 10-year bond eased to 6.3%.

Spain's bond market will be tested Thursday, when the government is due to auction up to €2 billion worth of 2-year, 4-year and 10-year bonds.